Over the last decade or so, aminoalkylindoles (AAIs) have attracted considerable attention as ligands of the cannabinoid CB1 and CB2 receptors. Various members of this group of compounds have been identified as either non-selective ligands, CB1 agonists, CB2 agonists, or as antagonists of these receptors (1-8). Various AAIs have also been suggested as being useful tools in pharmacological studies of cannabinoid ligands and cannabinoid receptors. Compounds, including AAIs, with activity at cannabinoid receptors have been suggested as being of use in a wide variety of therapeutic applications including anti-inflammatory, anti-glaucoma and immunosuppressant applications. One indication of particular interest for treatment by compounds with cannabinoid activity is pain therapy (5).
A typical example of the AAIs previously described is the generic structure provided as Formula I in U.S. Pat. No. 4,973,587where: C(═Z)-R3 is an arylcarbonyl group and Alk-N═B is a lower alkylene chain terminally substituted by a N,N-di-lower-alkylamino group, a 4-morpholinyl group, a 1-pyrrolidinyl or a 1-piperidinyl group.
Various structural modifications to this general structure have been explored, and one widely studied compound is designated as WIN-55212-2. WIN-55212-2 is structurally related to the other AAIs and includes an additional ring formed between the 7-position on the indole and C-1 of the alkyl chain at the 1-position on the indole core. 
A common structural feature of all of these previously reported AAIs is a carbonyl or thiocarbonyl group, further substituted by an aryl group, attached at the 3- or 4-position of the indole nucleus. Studies by Dutta et al. (1) pointed to the importance of the role of the keto group in the interaction of a number of AAIs with the cannabinoid receptor.
The present inventors have now surprisingly found that, in contrast to the findings by Dutta et al., the removal of the carbonyl group at C-3 of the indole nucleus and replacement thereof with a five membered heterocyclic group provides novel compounds which may exhibit useful activity at cannabinoid receptors.